Many industrial processes (e.g., harvesting salt from seawater, desalination plants, separating produced water from mine tailings, oil fracking processes, and other similar processes that produce waste water) generate large volumes of contaminated water that cannot be disposed of by draining it into the local watershed. The large volume of water combined with these contaminants makes it difficult/expensive to transport the waste water to a treatment facility. Removing the water from the contaminants would facilitate disposal by reducing the amount of waste needing to be managed. In other applications, water removal can also be used to attain a desirable good such as sea salt. In these situations, it is important to have an efficient and low cost method of removing the water to minimize production costs.
To address these issues, evaporation ponds are commonly used to concentrate materials by removing water. Evaporation ponds are artificial ponds with very large surface areas that expose a liquid mixture to air, solar radiation, and ambient temperatures. Exposure to ambient conditions causes the water to evaporate and contaminants or other materials that had been mixed with the water to be left in the pond. However, evaporation from these ponds is highly dependent on the ambient conditions. In order to have a sufficiently high evaporation rate, the surface area of the ponds needs to be very large, creating ponds that take up vast amounts of space. The large size of the ponds makes them expensive to construct and places constraints on where they can be built. Additionally, since the evaporation rate is related to the ambient temperature, little to no evaporation may take place in cold conditions.
In order to increase the evaporation rate from such ponds, sprayers can be used (where it is permitted) to shoot a mist of the pond water into the air. However, any contaminants in the pond are also sprayed into the air, and can be dispersed into the surrounding environment. In addition, sprayer systems have expensive operational costs due to the large power consumption required by the water pumps to create the water mist, and due to the required maintenance caused by scaling that develops on the spray nozzles.
What is needed, therefore, are improved techniques for increasing the evaporation rate of water from evaporation ponds.